Snap-in pivot pin for universal joints

ABSTRACT

A universal joint employs snap-in press pins to rotatably secure the center knuckle with the surrounding drive shaft cup providing a simplified assembly process. The press pins install flush or sub-flush with the outside of the steering shaft cup. A snap-lock feature permits one-direction axial movement only. Each snap pin includes a barb-like tapered flange with a lead-in ramp to aid installation. Once installed, a radially extending base on the backside of the flange abuts the inside wall of the drive shaft cup.

FIELD OF THE INVENTION

The present invention relates to the construction and assembly ofuniversal joints which inter-connect rotating shafts.

BACKGROUND OF THE INVENTION

Currently, a vehicle steering drive universal joint in a vehicle employstwo set screws that are affixed to an outer steering shaft cup. The setscrews each include a protruding pivot pin end that extends into thecentral pivoting ball. Unfortunately, there are several problems withthis current design. The high vibration environment and constanttwisting motion of the joint sometimes cause the set screws to loosenand subsequently fall free. Once the pin is loose, the steering drivemay disconnect, leaving a driver without the means to steer the vehicle.Additionally, the assembly process to install the set screws istime-consuming and expensive. The process requires greater time andexpense because both screw holes in the cup need to be tapped prior toassembly. The assembly cycle time is about 12 seconds which includesplacing the pin, threading the pin into the collar, hitting the pin witha wedge to mechanically lock the threads in place, rotating the assemblyand repeating the process for the second side.

SUMMARY OF THE INVENTION

The present invention reduces or eliminates the above-described failurerisk and as a secondary benefit, the assembly process is bothstreamlined and simplified. The present design replaces the set screwswith a snap-in press pin that installs flush or sub-flush with theoutside of the steering shaft. A snap lock feature permits one-directionmovement only. The pin snaps in but will not easily be pulled out. Likethe prior art screws, the press-in pin includes a pivot pin end that isfully rounded and protrudes into the center knuckle of the universaljoint. Once installed, the application end of the pin includes snap armswhich reside inside a hole of the outer cup of the joint. Thisconstruction is opposed by a similar pin/arm combination on the oppositeside of the steering shaft. The fastener may be composed of hardenedmetal for durability.

As further explained below, each snap pin includes a barb-like taperedflange with a lead-in ramp to aid installation. Once installed, aradially-extending base on the back side of the flange abuts the insidewall of the steering shaft cup. The flange base prevents removal of thepin because the pin can not be withdrawn unless it is first sheared off.In operation, a torque loading on the shaft and universal joint appliesonly a lateral shear force on the pin. The shear loading may push onesnap arm inwardly during extreme loading, but the pin will stay in placedue to the effect of the other three arms. Since no axial loadingoccurs, there is no direct loading that can force the pin to back out ofthe hole. Also, because the pin is flush or sub-flush with the outerwall of the shaft, it normally encounters no external force that cancompress the arms of the snap pin and cause it to disengage.

Because the pins are pressed into an unthreaded hole, the assemblyprocess is much simpler than using set screws. The parts are assembledwith an application of axial force pushing the pin's pivot end into thecenter knuckle until the snap flange travels completely through the wallof the shaft of the joint. This application of force can be a quickimpact load and because of the co-linear orientation of the parts acrossthe diameter of the shaft, the pins on both sides can be assembledsimultaneously with the same insertion force. This can be accomplishedextremely quickly and with inexpensive tooling without the need to tapthe hole. The fastener installs with an audible click as the flangesegments pass through the wall of the shaft and release outwardly fromtheir bent-inward position. At this position the fastener should beflush to the outer shaft wall. The combination of the flush alignmentand the audible feedback makes the installation process straightforwardand makes completion of installation simple to identify.

In this respect, before explaining at least one embodiment of theinvention in detail, it is to be understood that the invention is notlimited in its application to the details of construction and to thearrangements of the components set forth in the following description orillustrated in the drawings. The invention is capable of otherembodiments and of being practiced and carried out in various ways.Also, it is to be understood that the phraseology and terminologyemployed herein are for the purpose of description and should not beregarded as limiting.

As such, those skilled in the art will appreciate that the conception,upon which this disclosure is based, may readily be utilized as a basisfor the designing of other structures, methods, and systems for carryingout the several purposes of the present invention. It is important,therefore, that the claims be regarded as including such equivalentconstructions insofar as they do not depart from the spirit and scope ofthe present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a left side sectional view of the universal joint assembly ofthe invention.

FIG. 2 is a top front isometric view of the snap-in pin of theinvention.

FIG. 3 is a top plan view thereof.

FIG. 4 is a side elevation partial sectional view thereof

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to FIG. 1, the universal joint assembly of the inventionis shown in cross-section. A steering shaft 16 includes an outer cupstructure 11 at its end which pivotally holds a central knuckle element12 that in turn pivotally captures output shaft 13 about pin 14. Thedouble pivot axes located at the joints of pins 10 and 14 lie in thesame plane but are located at right angles to each other. Thisconfiguration is typical of a standard universal joint in whichrotational torque may be transmitted from one shaft to another whilepermitting a degree of angulation between the shafts. As explainedabove, the key aspect of the invention resides in the use of the novelpress pins 10 which replace the prior art set screws at the samelocation. The press-pin fastener 10 of the invention has two primarybody segments separated by a protruding flange. The bottom body portion1 is mostly solid and resides inside the central knuckle 12 while thetop body portion 15 is fully segmented by axial slots and resides withinone wall of the shaft 11.

Referring now to FIGS. 2, 3 and 4 as mentioned above, a top portion 15of the fastener 10 is comprised of a plurality of slots 7 that allow forthe compression of the flange 3 on each of four legs 2. An axial bore 8forms the bending legs of the fastener which can resiliently flexinwardly. The segmented flange 3 between the two body portions includesa ramp 4 on the side of the bottom body portion 1 to help compress thesegments of the flange during installation. A lead-in taper 5 aids ingetting the part started in the hole. After the flange 3 is compressedto a diameter less than the diameter of the hole in the steering shaftand passes completely through the wall of the shaft, it expands again.The side of the flange then resting against the backside wall of theshaft consists of a radially-extending base 6 to prevent the flangesegments from backing out of the shaft hole. Optionally, a relief groove9 can be added to the bottom portion to reduce the force required tobend the flange inward. The entire part should be hardened for minimalwear of the fastener-shaft interface.

Therefore, the foregoing is considered as illustrative only of theprinciples of the invention. Further, since numerous modifications andchanges will readily occur to those skilled in the art, it is notdesired to limit the invention to the exact construction and operationshown and described, and accordingly, all suitable modifications andequivalents may be resorted to, falling within the scope of theinvention.

1. A rotatable pivot joint, comprising: a rotatable driving shaftpivotably connected to a rotatable driven shaft by a pivot joint therebetween whereby rotation is transmitted from the driving shaft to thedriven shaft when there is an angular misalignment of the shafts; a cuplocated at a distill end of the driving shaft; said cup having opposingsides with opposite facing holes; a center knuckle lying between saidsides and being rotatably connected between said cup sides by a firstpair of pins extending inwardly by snap-fit retention through said holesin said sides; and said driven shaft being pivotably connected to saidcenter knuckle by a second pair of diametrically opposed pins extendingradially outward from said knuckle, said second pair of pins beingoffset radially 90° from said first pair of pins.
 2. The device of claim1 wherein said first pins are identical and each includes a solid bodyportion at a bottom insertion end with a plurality of inwardlydeflectable legs extending axially therefrom toward a opposite top end.3. The device of claim 2 further wherein each of said pins includes acentral axial bore located between said legs.
 4. The device of claim 3wherein each of said first pins includes axially extending slots locatedcircumferentially between adjacent legs of each of said pins.
 5. Thedevice of claim 4 wherein each of said first pins includes a segmentedflange having circumferential portions located along outer surfaces ofeach of said legs and extending radially therefrom.
 6. The device ofclaim 5 wherein each flange includes a ramp convergent toward the bottominsertion end of the pin.
 7. The device of claim 6 wherein each flangeincludes a radially extending base which sits against a backside wall ofthe shaft cup sides in which it is retained.